It will be appreciated that electronic control circuits especially microcomputers have the task of controlling several outputs in relationship to the voltage values at several inputs in accordance with a predetermined program. Heretofore, for example, control-keying-devices, terminal switches, or pickup devices were responsive to temperature and pressure are connected to the inputs. The output elements, such as, signal lamps, relays, timing circuits, or magnetic valves were connected to the outputs.
In connection with a specific area of application, such as, door control apparatus for buses and trains, it is necessary to take into consideration the numerous special demands of the traffic related industry. These are the different operating and functioning phases, additional blinkers, various numbers and types of doors, special alarm systems, among other things. Each type of door control demands a specific program for the microcomputer of the door control circuit. In order to satisfy these demands, up to now various types of electronic controls were utilized.
It is, for instance, possible to construct a universal electronic control circuit and equip it with a plug-in storage program unit or with a coding switch to set different programs. But, such a solution is too expensive if a large number of devices shall be produced.
The subject invention is based on the task of developing an electronic control of the aforementioned type which can be utilized for diversified special functions without additional extraneous logic-switching, such as, relays, pressure switches and delay circuits. Hereby, no switching of the control device shall be necessary for the respective request regarding special functions.
This problem is solved in the invention by providing an electronic control arrangement having a plurality of inputs and a plurality of outputs whereby the condition of the outputs is controlled in accordance with the condition of the inputs and whereby a control circuit sequentially interrogates the outputs in one-by-one fashion or in a serial order during a start-up test period. The outputs are coupled to a special-function line. The special-function line is connected to an additional input of the control circuit and the control circuit selects an appropriate stored program in accordance with the output signals on the special-function line. A significant advantage of the invention is contained in the fact that the electronic control system analyses the respective electrical state of the outputs and selects the corresponding given program. These outputs are connected to electrical elements which form the various external circuits. However, there can also be special diodes connected to the outputs for coding purposes.